Chapter 14 Exercises

1. Fix 5 errors in the code below so that it runs correctly. It will draw red and black horizontal stripes.

   from turtle import # use the turtle library from sys import * # use the system library setExecutionLimit(100000) # let this take up to 100 seconds space = screen() # create a turtle screen (space) width = space.window_width() # get the width of the screen (space) maxX = width / 2 # set the max x value to half the width sue = Turtle( # create a turtle named sue sue.pensize(10) # set the pen width for y in range(5): # repeat 5 times sue.penup() # pick up the pen if y % 2 == 0: # if even row sue.color('red') # set the color to red if y % 2 == 1: # if odd row sue.color('black') # set the color to black sue.goTo(-1 * maxX,y * 10) # move to the next row sue.pendown() # put the pen down sue.forward(width) # move forward by the width

   Add * at the end of line 1. Change line 4 to Screen. Add a ) at the end of line 9. Indent line 15. Change line 18 to goto.

   from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(100000) # let this take up to 100 seconds space = Screen() # create a turtle screen (space) width = space.window_width() # get the width of the screen (space) maxX = width / 2 # set the max x value to half the width sue = Turtle() # create a turtle named sue sue.pensize(10) # set the pen width for y in range(5): # repeat 5 times sue.penup() # pick up the pen if y % 2 == 0: # if even row sue.color('red') # set the color to red if y % 2 == 1: # if odd row sue.color('black') # set the color to black sue.goto(-1 * maxX,y * 10) # move to the next row sue.pendown() # put the pen down sue.forward(width) # move forward by the width

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2. The code below draws three peaks, vertically. Change 1 thing to make it draw three peaks horizontally. (Hint: You have to change something that’s in the body of the for loop)

   def draw(jaz, maxX): for x in range(3): jaz.forward(100) jaz.right(120) jaz.forward(100) jaz.left(120) if (jaz.xcor() <= maxX): jaz.penup() jaz.goto(-1 * maxX,jaz.ycor() - 100) jaz.pendown() def turtleSetup(width, jaz): space.setup(width,width) # set the space width and height maxX = width / 2 # set the max x value to half the width jaz.shape('turtle') jaz.penup() jaz.goto(-1 * maxX,100) jaz.pendown() jaz.left(60) draw(jaz, maxX) from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(50000) # let this take up to 50 seconds space = Screen() # create a turtle screen (space) jaz = Turtle() width = 400 turtleSetup(width, jaz)

   On line 7, change <= to >=.

   def draw(jaz, maxX): for x in range(3): jaz.forward(100) jaz.right(120) jaz.forward(100) jaz.left(120) if (jaz.xcor() >= maxX): jaz.penup() jaz.goto(-1 * maxX,jaz.ycor() - 100) jaz.pendown() def turtleSetup(width, jaz): space.setup(width,width) # set the space width and height maxX = width / 2 # set the max x value to half the width jaz.shape('turtle') jaz.penup() jaz.goto(-1 * maxX,100) jaz.pendown() jaz.left(60) draw(jaz, maxX) from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(50000) # let this take up to 50 seconds space = Screen() # create a turtle screen (space) jaz = Turtle() width = 400 turtleSetup(width, jaz)

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3. Indent lines in the code below so that it runs correctly. It will stamp 4 turtles in two different colors at the corners of a square.

   from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(100000) # let this take up to 100 seconds space = Screen() # create a turtle screen (space) width = space.window_width() # get the width of the screen (space) maxX = width / 2 # set the max x value to half the width sue = Turtle() # create a turtle named sue sue.shape("turtle") sue.penup() sue.left(45) for y in range(4): # repeat 4 times if y % 2 == 0: # if even row sue.color('red') # set the color to red if y % 2 == 1: # if odd row sue.color('black') # set the color to black sue.forward(100) sue.stamp() sue.backward(100) sue.left(90)

   Indent lines 15 to 22 as shown below.

   from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(100000) # let this take up to 100 seconds space = Screen() # create a turtle screen (space) width = space.window_width() # get the width of the screen (space) maxX = width / 2 # set the max x value to half the width sue = Turtle() # create a turtle named sue sue.shape("turtle") sue.penup() sue.left(45) for y in range(4): # repeat 4 times if y % 2 == 0: # if even row sue.color('red') # set the color to red if y % 2 == 1: # if odd row sue.color('black') # set the color to black sue.forward(100) sue.stamp() sue.backward(100) sue.left(90)

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4. Fix the errors so the turtle stays in a straight vertical line without leaving the screen.

   from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(50000) # let this take up to 50 seconds space = Screen() # create a turtle screen (space) height = 400 # set the desired height space.setup(height,height) # set the space width and height maxY = height / 2 # set the max y value to half the height t = Turtle() t.shape('turtle') for x in range(10): if (100 + t.ycor() > maxY): t.color("blue") t.left(180) t.backward(100) elif (t.ycor() - 100 > (-1* maxY)): t.color("red") t.left(180) t.forward(100) else t.color("green") t.forward(100)

   Fix the indentation first like below. Outside the for loop, turn the turtle 90 degrees. In the if statement, the turtle should go forward after turning. In the elif statement, the y position minus 100 should be less than the negative maxY. Make sure the else has a colon.

   from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(50000) # let this take up to 50 seconds space = Screen() # create a turtle screen (space) height = 400 # set the desired height space.setup(height,height) # set the space width and height maxY = height / 2 # set the max y value to half the height t = Turtle() t.shape('turtle') t.left(90) for x in range(10): if (100 + t.ycor() > maxY): t.color("blue") t.left(180) t.forward(100) elif (t.ycor() - 100 < (-1* maxY)): t.color("red") t.left(180) t.forward(100) else: t.color("red") t.forward(100)

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5. Fix 5 errors in the code below so that it runs correctly. It will draw a repeating pattern from left to right until it hits the width of the window and then will move back to the left side of the window to continue the pattern.

   def turtleLoop(jaz, maxX): for x in range(10): # repeat the body 10 times jaz.forward100) # go forward 100 jaz.right(120) # turn right 120 degrees jaz.forward(100) # go forward 100 jaz.left(120 # turn left 120 degrees if (jaz.xcor() >= maxX): # if at right edge of space jaz.penup() # pick up the pen jaz.goto(-1 * maxX,jaz.ycor() - 100) # move left & down jaz.pendown() # put the pen down def turtleProcedure(width, jaz): space.setup(width,width) # set the space width and height maxX = width / 2 # set the max x value to half the width jaz.shape('turtle') # set the shape for jaz to turtle jaz.penup() # pick up the pen (don't draw) jaz.goto(-1 * maxX,100) # go to the left side of the space jaz.penDown() # put the pen down to draw with jaz.left(60) # turn the turtle left 60 degrees turtleLoop(jaz, maxX) # call the other function from turtle * # use the turtle library from sys import * # use the system library setExecutionLimit(50000) # let this take up to 50 seconds Space = Screen() # create a turtle screen (space) width = 400 # set the desired width jaz = Turtle() # create a turtle named jaz turtleProcedure(width,jaz)

   Add import on line 23. Change line 26 to space. Change line 18 to pendown. Add a ( before the 100 on line 3. Add a ) on line 6.

   def turtleLoop(jaz, maxX): for x in range(10): # repeat the body 10 times jaz.forward(100) # go forward 100 jaz.right(120) # turn right 120 degrees jaz.forward(100) # go forward 100 jaz.left(120) # turn left 120 degrees if (jaz.xcor() >= maxX): # if at right edge of space jaz.penup() # pick up the pen jaz.goto(-1 * maxX,jaz.ycor() - 100) # move left & down jaz.pendown() # put the pen down def turtleProcedure(width, jaz): space.setup(width,width) # set the space width and height maxX = width / 2 # set the max x value to half the width jaz.shape('turtle') # set the shape for jaz to turtle jaz.penup() # pick up the pen (don't draw) jaz.goto(-1 * maxX,100) # go to the left side of the space jaz.pendown() # put the pen down to draw with jaz.left(60) # turn the turtle left 60 degrees turtleLoop(jaz, maxX) # call the other function from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(50000) # let this take up to 50 seconds space = Screen() # create a turtle screen (space) width = 400 # set the desired width jaz = Turtle() # create a turtle named jaz turtleProcedure(width,jaz)

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6. The code currently draws 5 horizontal lines of alternating colors. Change it so that it draws 5 vertical lines of alternating colors.

   from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(100000) # let this take up to 100 seconds space = Screen() # create a turtle screen (space) width = space.window_width() # get the width of the screen (space) maxX = width / 2 # set the max x value to half the width sue = Turtle() # create a turtle named sue sue.pensize(10) # set the pen width for y in range(5): # repeat 5 times sue.penup() # pick up the pen if y % 2 == 0: # if even row sue.color('yellow') # set the color to yellow if y % 2 == 1: # if odd row sue.color('black') # set the color to black sue.goto(-1 * maxX,y * 10) # move to the next row sue.pendown() # put the pen down sue.forward(width) # move forward by the width

   Change all the width to height, and flip the two parameters in the goto method. For ease of reading, you can switch all instances of x and y. Turn the turtle 90 degrees left before drawing.

   from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(100000) # let this take up to 100 seconds space = Screen() # create a turtle screen (space) height = space.window_height() # get the height of the screen (space) maxY = height / 2 # set the max y value to half the height sue = Turtle() # create a turtle named sue sue.pensize(10) # set the pen width sue.left(90) for x in range(5): # repeat 5 times sue.penup() # pick up the pen if x % 2 == 0: # if even row sue.color('yellow') # set the color to yellow if x % 2 == 1: # if odd row sue.color('black') # set the color to black sue.goto(x * 10,-1 * maxY) # move to the next row sue.pendown() # put the pen down sue.forward(height) # move forward by the height

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7. Change the code below to use if and else. Also fix any errors. You will need to change 3 lines. The code will draw random connected lines in alternating colors of red and black.

   from turtle import * # use the turtle library import random space = Screen() # create a turtle screen (space) width = space.window_width() height = space.window_height() maxX = width / 2 # get the max x value minX = -1 * maxX maxY = height / 2 minY = -1 * maxY jaz = Turtle() # create a turtle named jaz for num in range(10): if num % 2 == 0 # if even row jaz.color('red') # set the color to red if num % 2 == 1: # if odd row jaz.color('black') # set the color to black randX = random.randrange(minX, maxX) randY = random.randrange(minY, maxY) jaz.goto(randX,randY)

   Add a : at the end of line 12. Change line 14 to else:. Indent line 15.

   from turtle import * # use the turtle library import random space = Screen() # create a turtle screen (space) width = space.window_width() height = space.window_height() maxX = width / 2 # get the max x value minX = -1 * maxX maxY = height / 2 minY = -1 * maxY jaz = Turtle() # create a turtle named jaz for num in range(10): if num % 2 == 0: # if even row jaz.color('red') # set the color to red else: jaz.color('black') # set the color to black randX = random.randrange(minX, maxX) randY = random.randrange(minY, maxY) jaz.goto(randX,randY)

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8. Fix the errors in the code so it alternates between printing a horizontal yellow line and a vertical black line.

   from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(100000) # let this take up to 100 seconds space = Screen() # create a turtle screen (space) height = space.window_height() # get the height of the screen (space) width = space.window_width #get the width maxY = height / 2 # set the max y value to half the height maxX = width sue = Turtle() # create a turtle named sue sue.pensize(10) # set the pen width for x in range(4): # repeat 5 times sue.penup() # pick up the pen if x % 2 == 0: # if even row sue.color('yellow') # set the color to yellow sue.goto(-1 * maxX, x * 10) sue.penup() sue.forward(height) sue.left(90) if x % 2 == 1: # if odd row sue.color('black') # set the color to black sue.goto(x * 10,-1 * maxY) sue.pendown() sue.forward(height) sue.left(90)

   Fix the indentation. In the if statement for even, it should be pendown() and it should go forward the height. In the odd if statement, it should turn right.

   from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(100000) # let this take up to 100 seconds space = Screen() # create a turtle screen (space) height = space.window_height() # get the height of the screen (space) width = space.window_width() #get the width maxY = height / 2 # set the max y value to half the height maxX = width / 2 sue = Turtle() # create a turtle named sue sue.pensize(10) # set the pen width for x in range(4): # repeat 5 times sue.penup() # pick up the pen if x % 2 == 0: # if even row sue.color('yellow') # set the color to yellow sue.goto(-1 * maxX, x * 10) sue.pendown() sue.forward(width) sue.left(90) if x % 2 == 1: # if odd row sue.color('black') # set the color to black sue.goto(x * 10,-1 * maxY) sue.pendown() sue.forward(height) sue.right(90)

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9. Fix the indention so that the code runs correctly. Two turtles will move towards each other and then turn around and move away from each other.

   from turtle import * space = Screen() jaz = Turtle() mia = Turtle() mia.color('red') mia.penup() mia.goto(100,0) mia.pendown() mia.right(180) for x in range(20): jaz.forward(10) mia.forward(10) if (mia.xcor() - jaz.xcor() < 40): jaz.right(45) mia.right(45)

   Indent lines 11-15 as shown below.

   from turtle import * space = Screen() jaz = Turtle() mia = Turtle() mia.color('red') mia.penup() mia.goto(100,0) mia.pendown() mia.right(180) for x in range(20): jaz.forward(10) mia.forward(10) if (mia.xcor() - jaz.xcor() < 40): jaz.right(45) mia.right(45)

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10. Change and fix the code below so that it draws random, but connected black and red lines (it should look like scribbling) only in the bottom right half of the drawing window.

    from turtle import * # use the turtle library import random space = Screen() # create a turtle screen (space) width = space.window_width() height = space.window_height() maxX = width / 2 # get the max x value minX = -1 * maxX maxY = height / 2 minY = -1 * maxY jaz = Turtle() # create a turtle named jaz for num in range(10): if num % 2 == 0 # if even row jaz.color('red') # set the color to red if num % 2 == 1 # if odd row jaz.color('black') # set the color to black randX = random.randrange(minX, maxX) randY = random.randrange(minY, maxY) jaz.goto(randX,randY)

    Fix the indentation and add colons after the if statements. Change the range of randX to be (0, maxX) and the range of randY to be (minY, 0).

    from turtle import * # use the turtle library import random space = Screen() # create a turtle screen (space) width = space.window_width() height = space.window_height() maxX = width / 2 # get the max x value minX = -1 * maxX maxY = height / 2 minY = -1 * maxY jaz = Turtle() # create a turtle named jaz for num in range(10): if num % 2 == 0: # if even row jaz.color('red') # set the color to red if num % 2 == 1: # if odd row jaz.color('black') # set the color to black randX = random.randrange(0,maxX) randY = random.randrange(minY, 0) jaz.goto(randX,randY)

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11. The following code stamps a circle of turtles. Change the following code to use a different color per stamp and use at least 3 colors. You can use a counter and reset the counter to 0 after it reaches the number of colors (i.e. use a for loop and change color based off divisibility of each number). Use if, elif, and else.

    from turtle import * space = Screen() jose = Turtle() jose.shape("turtle") jose.penup() for size in range(10): jose.forward(50) jose.stamp() jose.forward(-50) jose.right(36)

    Add lines 7-12 as shown below.

    from turtle import * space = Screen() jose = Turtle() jose.shape("turtle") jose.penup() for size in range(10): if (size % 3 == 0): jose.color('blue') elif (size % 3 == 1): jose.color('yellow') else: jose.color('gray') jose.forward(50) jose.stamp() jose.forward(-50) jose.right(36)

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12. Add to the code so that num is a random number between 1 and 3 (inclusive), and change the if clauses to be if, elif, and else. The code should draw random lines with 3 different colors based off the value of num.

    from turtle import * # use the turtle library import random space = Screen() # create a turtle screen (space) width = space.window_width() height = space.window_height() maxX = width / 2 # get the max x value minX = -1 * maxX maxY = height / 2 minY = -1 * maxY jaz = Turtle() # create a turtle named jaz for x in range(10): num = if num % 3 == 0: # if even row jaz.color('red') # set the color to red if num % 2 == 1: # if odd row jaz.color('black') # set the color to black if num % 1 == 2: jaz.color('blue') randX = random.randrange(minX, maxX) randY = random.randrange(minY, maxY) jaz.goto(randX,randY)

    from turtle import * # use the turtle library import random space = Screen() # create a turtle screen (space) width = space.window_width() height = space.window_height() maxX = width / 2 # get the max x value minX = -1 * maxX maxY = height / 2 minY = -1 * maxY jaz = Turtle() # create a turtle named jaz for x in range(10): num = random.randrange(1,4) if num % 3 == 0: # if even row jaz.color('red') # set the color to red elif num % 2 == 1: # if odd row jaz.color('black') # set the color to black else: jaz.color('blue') randX = random.randrange(minX, maxX) randY = random.randrange(minY, maxY) jaz.goto(randX,randY)

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13. The following code stamps turtles in a spiral. Change the code below to cycle through at least 3 colors. Use if, elif, and else.

    from turtle import * space = Screen() tess = Turtle() tess.shape("turtle") tess.penup() # ask tess to pick up her pen for size in range(5, 60, 2): # start with size = 5 and grow by 2 tess.stamp() # leave an impression on the canvas tess.forward(size) # move tess along tess.right(24) # and turn her

    Add lines 7-12 as shown below.

    from turtle import * space = Screen() tess = Turtle() tess.shape("turtle") tess.penup() # ask tess to pick up her pen for size in range(5, 60, 2): # start with size = 5 and grow by 2 if (size % 3 == 0): tess.color('blue') elif (size % 3 == 1): tess.color('yellow') else: tess.color('gray') tess.stamp() # leave an impression on the canvas tess.forward(size) # move tess along tess.right(24) # and turn her

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14. The code currently makes the two turtles just draw a circle. Fix the errors on line 13 so that the turtles move towards each other and then turn around and move away from each other.

    from turtle import * space = Screen() jaz = Turtle() mia = Turtle() mia.color('red') mia.penup() mia.goto(100,0) mia.pendown() mia.right(180) for x in range(20): jaz.forward(10) mia.forward(10) if (mia.xcor() + jaz.xcor() > 40): jaz.right(45) mia.right(45)

    The if statement should be mia.xcor() - jaz.xcor() < 40.

    from turtle import * space = Screen() jaz = Turtle() mia = Turtle() mia.color('red') mia.penup() mia.goto(100,0) mia.pendown() mia.right(180) for x in range(20): jaz.forward(10) mia.forward(10) if (mia.xcor() - jaz.xcor() < 40): jaz.right(45) mia.right(45)

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15. The following code draws vertical stripes alternating between red and black. Change and add code below to use 5 different colors. Use y % 5 instead of y % 2 to get 5 possible values.

    from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(100000) # let this take up to 100 seconds space = Screen() # create a turtle screen (space) width = space.window_width() # get the width of the screen (space) maxX = width / 2 # set the max x value to half the width sue = Turtle() # create a turtle named sue sue.pensize(10) # set the pen width for y in range(10): # repeat 10 times sue.penup() # pick up the pen if y % 2 == 0: # if even row sue.color('red') # set the color to red if y % 2 == 1: # if odd row sue.color('black') # set the color to black sue.goto(-1 * maxX,y * 10) # move to the next row sue.pendown() # put the pen down sue.forward(width) # move forward by the width

    Modify lines 15 and 17 as shown below. Add lines 18 to 23.

    from turtle import * # use the turtle library from sys import * # use the system library setExecutionLimit(100000) # let this take up to 100 seconds space = Screen() # create a turtle screen (space) width = space.window_width() # get the width of the screen (space) maxX = width / 2 # set the max x value to half the width sue = Turtle() # create a turtle named sue sue.pensize(10) # set the pen width for y in range(10): # repeat 10 times sue.penup() # pick up the pen if y % 5 == 0: sue.color('red') # set the color to red if y % 5 == 1: sue.color('black') if y % 5 == 2: sue.color('orange') if y % 5 == 3: sue.color('green') if y % 5 == 4: sue.color('blue') sue.goto(-1 * maxX,y * 10) # move to the next row sue.pendown() # put the pen down sue.forward(width) # move forward by the width

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16. Complete and add to the turtleLoop procedure so that when the turtles collide, they move away, then turn so that they move in the same direction. It should look like a mirror image divided across the vertical axis.

    def turtleLoop(jaz,mia): for x in range(20): jaz.forward(10) mia.forward(10) if (mia.xcor() - jaz.xcor() < 30): def turtleDraw(jaz, mia): jaz.shape('turtle') mia.shape('turtle') mia.color('red') mia.penup() mia.goto(100,0) mia.pendown() mia.right(180) turtleLoop(jaz,mia) from turtle import * space = Screen() jaz = Turtle() mia = Turtle() turtleDraw(jaz,mia)

    Complete like shown below.

    def turtleLoop(jaz,mia): for x in range(20): jaz.forward(10) mia.forward(10) if (mia.xcor() - jaz.xcor() < 30): jaz.backward(50) mia.backward(50) jaz.right(45) mia.left(45) def turtleDraw(jaz, mia): jaz.shape('turtle') mia.shape('turtle') mia.color('red') mia.penup() mia.goto(100,0) mia.pendown() mia.right(180) turtleLoop(jaz,mia) from turtle import * space = Screen() jaz = Turtle() mia = Turtle() turtleDraw(jaz,mia)

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17. Write a function takes a number and returns a color. It will return ‘yellow’ if the number modulus 3 is 0, ‘blue’ if it is 1, and ‘green’ if it is 2.

    Define the function as shown below and be sure to create tests that try all possible execution paths (all return values).

    def getColor(num): if num % 3 == 0: return 'yellow' elif num % 3 == 1: return 'blue' else: return 'green' print(getColor(3)) print(getColor(4)) print(getColor(5)) print(getColor(6))

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18. Write a procedure that takes in any number as the first parameter and a turtle as another parameter. The procedure should determine if the number is even or odd. If it is even have the turtle go right. If it is odd, have it go left. The procedure should get a random value between 1 and 2 (inclusive) and assign a color based on that number.

    Define the procedure as shown below. Don’t forget to import the necessary modules.

    def turtleDraw(num, turtle): rand = random.randrange(1,3) if rand == 1: turtle.color("blue") else: turtle.color("red") if num % 2 == 0: turtle.forward(100) else: turtle.left(180) turtle.forward(100) from turtle import * import random space = Screen() jaz = Turtle() turtleDraw(10, jaz)

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19. Write code that draws a pattern with the turtle with at least 3 different colors used. The code must have a for loop and must have a if statement inside the for loop that changes the color.

    Below is one possible example. Look for a for loop with an if statment inside of it that changes the color.

    from turtle import * space = Screen() jose = Turtle() for size in range(9): if (size % 3 == 0): jose.color('green') elif (size % 3 == 1): jose.color('blue') else: jose.color('yellow') jose.forward(50) jose.forward(-50) jose.right(40)

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20. Write code that uses 2 turtles and a for loop to get a range of numbers. You should change the color of the based off if the number from the for loop is even or odd. The two turtles should move towards each other but turn away and move when they are about to intersect.

    Here’s an example of one possibility.

    from turtle import * space = Screen() jaz = Turtle() mia = Turtle() mia.penup() mia.goto(100,0) mia.pendown() mia.right(180) for x in range(20): if x % 2 == 0: mia.color("blue") jaz.color("green") else: mia.color("red") jaz.color("yellow") jaz.forward(10) mia.forward(10) if (mia.xcor() - jaz.xcor() < 40): jaz.right(45) mia.right(45)

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